Plasma processing chamber for bevel edge processing

ABSTRACT

A process chamber includes a wafer support to mount a wafer to be processed in the process chamber, with the wafer having an annular edge exclusion area. A first electrically grounded ring extends in an annular path radially outward of the edge exclusion area and is electrically isolated from the wafer support. A second electrode is configured with a center area opposite to the wafer support. A second electrically grounded ring extends in an annular path radially outward of the second electrode and the edge exclusion area. The second electrically grounded ring is electrically isolated from the center area. An annular mount section has a DC bias ring, and the DC bias ring opposes the edge exclusion area when the wafer is present. A DC control circuit is provided for applying a DC voltage to the DC bias ring.

CLAIM OF PRIORITY

This is a divisional of U.S. patent application Ser. No. 13/870,917,filed on Apr. 25, 2013, entitled “Plasma Processing Chamber for BevelEdge Processing,” which is a divisional of U.S. patent application Ser.No. 13/082,393, filed on Apr. 7, 2011, now U.S. Pat. No. 8,440,051 B2,entitled “Plasma Processing Chamber for Bevel Edge Processing,” which isa divisional of U.S. patent application Ser. No. 11/818,621, filed onJun. 14, 2007, now U.S. Pat. No. 8,268,116 B2, entitled “Methods of andApparatus for Protecting a Region of Process Exclusion Adjacent to aRegion of Process Performance in a Process Chamber.” The disclosures ofthese applications from which priority is claimed are incorporatedherein by reference for all purposes.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to U.S. patent application Ser. No.11/701,854, filed on Feb. 2, 2007, now U.S. Pat. No. 7,575,638 B2, andentitled “Apparatus for Defining Regions of Process Exclusion andProcess Performance in a Process Chamber.” The disclosure of thisrelated application is incorporated herein by reference for allpurposes.

BACKGROUND

Vacuum processing chambers have been used for etching materials fromsubstrates and for deposition of materials onto substrates. Thesubstrates have been semiconductor wafers, for example. In general,accurate processing (and thus high yields of active devices) is expectedto occur in a central area of the wafer (i.e., in an active deviceregion). Numerous difficulties are experienced in attempting toaccurately process the wafer between the central area and a peripheraledge of the wafer that surrounds the central area on a top, or upper,surface of the wafer that is to be processed to form the devices. Suchdifficulties are significant enough that an “edge exclusion area” hasbeen defined between the central area and that edge of the wafer. Noattempt is made to provide acceptable devices in that edge exclusionarea.

Additionally, during the desired processing of the central area,undesired deposits, materials, or process-by-products (collectively“undesired materials”) accumulate or result on the edge exclusion areaof the upper surface of the wafer, and on a beveled edge area around theperipheral edge of the wafer, and below the beveled edge area onto abottom area of an opposite (bottom) surface of the wafer. The edgeexclusion area, the beveled edge area, and the bottom area are referredto herein collectively as the “edge environ”. The edge environ is not tobe processed to form devices. These undesired materials may generallyaccumulate on the edge environ. In general, it is desired to keep theedge environ substantially clean, so as to avoid flaking of materialparticulates that may redeposit back onto the active device regions onthe upper surface of the wafer. Such flaking can occur during any numberof wafer handling or transport operations, and thus, it is a generaldesire that the edge environ be periodically cleaned (e.g., etched) toremove the undesired materials from the processed wafers. During aremoval, or cleaning, process the edge environ is a region of process(cleaning) performance, and the central area of the active devices is aregion of process exclusion.

In view of the foregoing, there are needs for methods and apparatus forremoving the undesired materials from only the edge environ and notdamaging the central area.

SUMMARY

Broadly speaking, embodiments of the present invention fill these needsby providing ways of protecting the central area so that during theremoving of the undesired materials from only the edge environ thecentral area is not damaged. The ways preferably include use of electricand magnetic field strengths configured to protect the central area fromcharged particles from plasma in a process chamber. Such field strengthsfoster removal of the undesired materials from only the edge environ. Inone embodiment, the magnetic field is configured with a peak locatedadjacent to a border between the central area and the edge environ, andthe configuration provides a strong gradient extending from the peakradially away from the border and away from the central area to repelthe charged particles from crossing the border.

It should be appreciated that the present invention can be implementedin numerous ways, including as an apparatus, a method and a system.Several inventive embodiments of the present invention are describedbelow.

In one embodiment, chambers for processing a bevel edge of a substrateare provided. One such chamber includes a bottom electrode defined tosupport a substrate in the chamber. The bottom electrode has a bottomfirst level for supporting the substrate and a bottom second level nearan outer edge of bottom electrode. The bottom second level is defined ata step below the bottom first level. Further included is a top electrodeoriented above the bottom electrode. The top electrode having a topfirst level and a top second level, where the top first level isopposite the bottom first level and the top second level is opposite thebottom second level. The top second level is defined at a step above thetop first level. A bottom ring mount oriented at the bottom second levelis included. The bottom ring mount includes a first adjuster for movinga bottom permanent magnet toward and away from the top electrode.Further included is a top ring mount oriented at the top second level.The top ring mount includes a second adjuster for moving a top permanentmagnet toward and away from the bottom electrode.

In one embodiment, apparatus is provided for protecting a central areaof a wafer from charged particles in a process chamber. A firstelectrode is configured to mount the wafer in the process chamber withthe central device area within a device border centered on a wafer axisand with a wafer edge exclusion area extending radially away from boththe axis and the border. A second electrode is configured with a fieldring mount section extending radially from the border and away from theaxis and being located adjacent to the border. A field ring arrangementis configured to establish a field capable of exerting force on thecharged particles to repel the particles from moving to the centraldevice area. The field ring arrangement is mounted in the field ringmount section and is configured so that the field has a field strengthgradient configured with a peak value adjacent to the border. The fieldstrength gradient defines increasing field strength inverselyproportional to increased radial distance away from the axis and awayfrom the border. The gradient and the peak value of the field strengthrepel the charged particles from moving radially past the border towardthe axis.

In another embodiment, apparatus for protecting a central area of awafer from charged particles in a process chamber may include a firstelectrode configured to mount the wafer in the process chamber. Themounting is with the central area within a circular wafer bordercentered on a wafer axis and with a wafer edge exclusion area extendingradially relative to the axis and outside the border. The firstelectrode may be further configured with a first ring mount section. Asecond electrode may be configured with a second ring mount sectionextending radially relative to the border and away from the axis. Aring-shaped permanent magnet arrangement may be configured with a firstpermanent magnet section mounted in the first ring mount section and asecond permanent magnet section mounted in the second ring mountsection. The first and second mounted permanent magnet sections may beconfigured to establish a magnetic field that extends axially betweenthe first and second mounted permanent magnet sections and in an annularpath centered on the axis. The first and second mounted permanent magnetsections may be further configured to establish the magnetic fieldconfigured with a magnetic field strength that is uniform around thewafer axis and that has a field strength gradient that varies withrespect to radial distance relative to the axis and away from theborder. The gradient variation may be from a peak value located adjacentto the border and inversely proportional to increased radial distanceaway from the axis. The gradient and the peak value of the fieldstrength may be configured to repel the charged particles from movingradially past the border toward the axis.

In yet another embodiment, apparatus may protect a central area of awafer from charged particles in a process chamber. A first electrode maybe configured with a wafer support to mount the wafer to be processed inthe process chamber, the wafer being configured with an axis and thecentral area being defined by a circular border centered on the axis.The border may be configurable at any of a plurality of radial distancesrelative to the axis and be surrounded by an annular edge exclusionarea. The first electrode may be further configured with a firstelectrically grounded ring extending in an annular path radially outwardof the edge exclusion area and electrically isolated from the wafersupport. Different configurations of the edge exclusion area may bedefined by the border positioned at different ones of the plurality ofradial distances relative to the axis. A second electrode may beconfigured with a center area opposite to the central area and with afirst annular mount section aligned with the border. The secondelectrode may be further configured with a second electrically groundedring extending in an annular path radially outward of the edge exclusionarea and electrically isolated from the center area and from the firstannular mount section. The first annular mount section may beelectrically isolated from the center area. A DC bias ring is secured tothe first annular mount section to establish an electric field in theprocess chamber. The DC bias ring is configured so that the electricfield extends away from the circular border and across the edgeexclusion area to each of the first and second grounded rings to repelthe charged particles from crossing the border and promote etching ofthe edge exclusion area. A DC control circuit applies a DC voltage tothe DC bias ring, a value of the DC voltage being directly proportionalto a value of the radial distance of the border relative to the axis

In still another embodiment, a method protects the central area of thewafer from charged particles during etching of the edge exclusion areasurrounding the circular border that defines the central area. Anoperation may mount the wafer in an etching chamber with the edgeexclusion area extending in a radial direction outside the border.Another operation may establish a constant magnetic field betweenopposite permanent magnet polarities so that a peak value of magneticfield strength is adjacent to the border and the magnetic field strengthdecreases suddenly from the peak value with increased distance away fromthe border and from the axis. The peak value of the magnetic field andsudden decrease of the magnetic field strength repel movement of chargedparticles past the border to the central region and promote bombardmentof the edge exclusion area by the repelled particles.

In another embodiment, a process chamber includes a wafer support tomount a wafer to be processed in the process chamber, with the waferhaving an annular edge exclusion area. A first electrically groundedring extends in an annular path radially outward of the edge exclusionarea and is electrically isolated from the wafer support. A secondelectrode is configured with a center area opposite to the wafersupport. A second electrically grounded ring extends in an annular pathradially outward of the second electrode and the edge exclusion area.The second electrically grounded ring is electrically isolated from thecenter area. An annular mount section has a DC bias ring, and the DCbias ring opposes the edge exclusion area when the wafer is present. ADC control circuit is provided for applying a DC voltage to the DC biasring.

In one embodiment, a first insulator ring is disposed between the wafersupport and the first electrically grounded ring, and a second insulatorring is disposed between the second electrode and the secondelectrically grounded ring. In one embodiment, the DC control circuitapplies a positive DC voltage to establish an electric field.

Other aspects of the invention will become apparent from the followingdetailed description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements.

FIG. 1 shows a schematic plan view of one-quarter of a substrate onwhich accurate processing (and thus high yields of active devices) isexpected to occur in a central area of a top surface of the substrate.

FIG. 2 shows a schematic elevational view of the substrate of FIG. 1.

FIG. 3 is a schematic view showing an embodiment of apparatus of thepresent invention for cleaning an edge environ of the substrate whileprotecting the central area.

FIG. 4A is an enlarged schematic view of a portion of FIG. 3,illustrating a tendency of charged particles to move in response to biason the substrate without embodiments of the present invention.

FIG. 4B is an enlarged schematic view of the apparatus of FIG. 3,further configured with a lower electrode configured to mount thesubstrate in a process chamber and with an upper electrode configured toprotect the central area.

FIG. 5 is a graph showing field strength of a field resulting from afield ring arrangement vs. distance in a direction extending radiallyfrom an axis of the substrate.

FIG. 6 is a schematic elevational view showing one embodiment of amagnetic field embodiment of the field ring arrangement.

FIG. 7 is a schematic view similar to FIG. 6, showing an embodiment ofapparatus with one or both of first and second ring mount sectionsconfigured to adjustably mount first and second permanent magnetsections for movement relative to each other in a direction parallel tothe axis.

FIG. 8 is a graph showing field strength of a field resulting from afield ring arrangement vs. distance in a direction extending radiallyfrom the axis, wherein the field is configured so that a field strengthgradient varies as shown by exemplary curves.

FIG. 9 illustrates configurations of first and second permanent magnetsections to control the location of a peak path of the magnetic fieldbetween the magnet sections according to a desired extent of radialmovement of charged particles across top and bottom surfaces of thesubstrate.

FIG. 10 is a schematic view showing an embodiment of the apparatus ofFIG. 3, in which a field ring mount section and a field ring arrangementare configured to establish an electric field for protecting the centralarea of the substrate from the charged particles in the process chamber.

FIG. 11 is a diagram showing a flow chart, illustrating operations of amethod of protecting the central area of the substrate from chargedparticles during etching.

FIG. 12 is a diagram showing a flow chart, illustrating operations of amethod for controlling a value of peak magnetic field strength of amagnetic field that extends through the substrate at the edge exclusionarea, the control being according to a radial location of a border withrespect to a central axis of the substrate.

FIG. 13 is a diagram showing a flow chart, illustrating operations of amethod that controls a location of a peak path of a magnetic fieldbetween sections of magnets according to a desired extent of radialmovement of charged particles across top and bottom surfaces of thesubstrate.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of embodiments of the presentinvention. It will be apparent, however, to one skilled in the art thatthe present invention may be practiced without some or all of thesespecific details. In other instances, well known process operations havenot been described in detail in order not to obscure the presentinvention.

With the above considerations in mind, the following will define severalexemplary circuit and system configurations. However, it should beunderstood that modifications may be possible, as defined by theappended claims. Specifically, although reference is made to certaincircuit designs, it should be understood that the functionality can beimplemented in a number of forms. For instance, the functionalityperformed by circuits (e.g., analog and digital), can be re-renderedinto firmware. Additionally, firmware can be executed alone or inconjunction with software control or assistance to complete or partiallycomplete processing steps or communication.

Embodiments of an invention are described for apparatus, systems foruse, and methods for protecting an edge environ of a substrate such as asemiconductor wafer, so that during the removing of undesired materialsfrom only the edge environ a central area of the wafer is not damaged.In these embodiments, electric and magnetic field strengths may beconfigured to protect the central area from charged particles fromplasma in a process chamber. The field strengths foster removal of theundesired materials from only the edge environ. In another embodiment,the magnetic field is configured with a peak located adjacent to aborder between the central area and the edge environ, and theconfiguration provides a strong magnetic field gradient extending fromthe peak radially away from the border and away from the central area torepel the charged particles from crossing the border.

The word “substrate,” as used herein, denotes without limitation,semiconductor wafers, hard drive disks, optical discs, glass substrates,and flat panel display surfaces, liquid crystal display surfaces, etc.,on which materials or layers of various materials may be formed ordefined in a processing chamber, such as a chamber in which a plasma isestablished for processing, e.g., etching or deposition.

For each type of substrate (also referred to herein as a “wafer”),accurate processing (and thus high yields of active devices) is expectedto occur in the central area of the top surface of the substrate. Thecentral area may be defined by a border, such as an exemplary circularborder centered on a center axis of the substrate. The border may thusencompass the central area on which the devices are intended to beformed. The border may also indicate an annular area on the top surface,the annular area being radially outward from the border and extending toa bevel that is next to an outer edge of the substrate. The annular areasurrounds the border, is not to be processed to form devices, and isreferred to as the “edge exclusion area”. The “edge environ” of thesubstrate collectively refers to the edge exclusion area, the bevel, theouter edge, and a bottom area under the top surface. During the desiredprocessing of the central area to form the desired active devices, theundesired materials may accumulate on the edge environ. To avoid flakingof material particulates that may redeposit back onto active deviceregions on the central area, embodiments of the present invention may beused to periodically clean (e.g., etch) the undesired materials from theedge environ of the processed substrates.

FIG. 1 shows a schematic plan view of one-quarter of a substrate 30 onwhich accurate processing (and thus high yields of active devices 31) isexpected to occur in a central area 32 of a top surface 34 of thesubstrate. The central area 32 may be defined by a border 36, such as anexemplary circular border centered on a center axis 38 of the substrate30. Other shapes of the central area 32 may be provided, for example,but in each case the border 36 may encompass (or enclose) the centralarea 32 on which the devices 31 are intended to be formed. The border 36also indicates (or serves to define) another area 40 on the top surface34. When the substrate 30 is a semiconductor wafer, for example, thearea 40 may be annular, centered on the axis 38, and extend radiallyoutward from the border 36 to a bevel 42 next to an outer edge 44 of thesubstrate. Other shapes of the area 40 may be provided, for example, butin each case the other area 40 is an area on which no devices 31 are tobe formed. The border 36 is used herein to define a line of transitionbetween the central (active device) area 32 and the other (no device)area 40. The other area 40 surrounds the border 36, and is referred toherein as the “edge exclusion area”. The edge exclusion area 40, thebevel 42, the outer edge 44, and a bottom surface 46 (FIG. 2) under thetop surface 34 are included in the “edge environ” 48 of the substrate30.

The word “axial” as used herein defines a direction parallel to the axis38, and is also used in the form of “axially” to define an itemextending in the axial direction (i.e., extending parallel to the axis38). The word “radial” as used herein defines a direction perpendicularto and centered on the axis 38, and is also used in the form of“radially” to define a radius extending perpendicular to the axialdirection (i.e., extending perpendicular to the axis 38).

FIG. 2 shows a schematic elevational view of the substrate 30. FIGS. 1and 2 illustrate that during the desired processing of the central area32 to form the desired active devices 31, undesired materials 50 mayaccumulate on the edge environ 48. To avoid flaking of materialparticulates that may redeposit back onto the active devices 31 on thecentral area 32, embodiments of the present invention may be used toperiodically clean (e.g., etch) the undesired materials 50 from the edgeenviron 48 of the processed substrates 30. FIG. 3 is a schematic viewshowing an embodiment of apparatus 60 of the present invention for suchcleaning, which protects the central area 32 of the substrate 30. Duringthe removing of the undesired materials 50 from only the edge environ48, the central area 32 is not damaged.

FIG. 3 shows the apparatus 60 including a vacuum processing chamber 62having a substrate holder, or lower electrode, 64 providing a suitableclamping force to the substrate 30. The top of the chamber 62 may beprovided with a chamber window, such as a dielectric window, 68. A port70 is shown provided in the window 68 to permit access to the interiorof the chamber 62. FIG. 3 also schematically shows the chamber 62provided with facilities 74 that require access to the chamber 62 viathe port 70. The facilities 74 may require such access to facilitateconducting deposition or etching or implantation processes in thechamber 62, such as by supplying process gases to the chamber. As oneexample of the facilities 74, process gases may be supplied from one ormore gas supplies through the port 70 into the chamber 62. A pump (notshown) may reduce the pressure in the chamber 62 to a pressure in anexemplary range of 1 to 1000 milliTorr.

For removing the undesired materials 50 from only the edge environ 48 byan etching process, for example, a first source 78 of RF energy with animpedance matching circuit may be connected to a coil 80 to energize thegas in the chamber and maintain a high density (e.g., 10⁻¹¹ to 10⁻¹²ions/cm3) plasma in the chamber 62. The coil 80 may be operated at atypical fixed frequency of 13.56 MHz, and may be a type that inductivelycouples RF energy into the chamber 62 through the window 68 to providethe high-density plasma for conducting the processes in the chamber 62.During that coupling, the coil 80 generates an electric field (see lines82, FIG. 3). FIG. 3 also shows that for process control, such ascontrolling the etching, second RF power is separately communicated tothe chamber by a second RF source 84. The source 84 may include amatching network comprising variable reactances, and the matched secondRF power is applied to the lower electrode 64 in the form of a second RFsignal 88. The variable reactances of the matching network arecontrolled to match the impedance of the second RF signal 88 to theimpedance of the lower electrode 64. The load coupled to the lowerelectrode 64 is primarily the plasma in chamber 62. The second RF signal88 applied to the lower electrode 64 interacts with charged particles 90(FIG. 4A) in the plasma to bias the substrate 30.

FIG. 4A is an enlarged schematic view of a portion of FIG. 3,illustrating a tendency of the charged particles 90 to move in responseto such bias on the substrate 30. Exemplary charged particles 90 areshown moving in the process chamber 62 toward the axis 38, and movingacross the edge exclusion area 40 and past the border 36 to the centralarea 32 and the active devices 31 that are to be protected. Particles 90are also shown moving under the bottom surface 46 past a circularperimeter 92 that defines the portion of the bottom surface 46 that iswithin the edge environ 48. Such moving would occur without theembodiments of the present invention. Without the embodiments, theparticles 90 would bombard and cause removal of material 31D from thedevices 31, such that damage to the devices 31 may result.

In a general sense, FIG. 4B shows that to protect the central area 32,the apparatus 60 may be further configured with the lower, or first,electrode 64 configured to mount the substrate 30 in the process chamber62 with the central device area 32 within the border 36 that is centeredon the wafer axis 38. As so mounted, the wafer edge exclusion area, orexclusion area, 40 (FIG. 2) extends radially away from both the axis 38and the border 36. A second (or upper) electrode 86 may be configuredwith a field ring mount section 94 (also referred to as a second, orupper ring mount, section). Section 94 extends radially relative to theborder 36 and away from the axis 38. A field ring arrangement 96 may beconfigured to establish a field 97 having a return path 98 and a peakpath 99. The field 97 in the peak path 99 is capable of exerting forceFR on the charged particles 90 to repel the particles 90 from moving tothe central device area 32 (i.e., repel the particles 90 from moving asshown in FIG. 4A, wherein such moving may cause damage to the devices31). The field ring arrangement 96 is mounted in the field ring mountsection 94 and is configured so that the field 97 has a field strengthgradient G between the return path 98 and the peak path 99. Gradient Gis configured so that the peak path 99 having a peak field strengthvalue P extends adjacent to the border 36. As used herein, “adjacent”relates to a location of the peak path 99 relative to the border 36, andin particular to the peak path 99 located in a position within a rangeof locations, the locations being from a location at the border 36 to alocation 4 mm radially outward of the border 36. In a preferredembodiment, the peak path 99 is located in that range at a distance of 2mm radially outward of the border 36.

The field ring arrangement 96 may be further configured to establish thepeak path 99 extending adjacent to the border 36 with the gradient Gdefining increasing field strength inversely proportional to increasedradial distance of the paths 98 and 99 away from the axis 38 and awayfrom the border 36. With this configuration of the field ringarrangement 96, the gradient G and the peak value P of the fieldstrength of the peak path 99 repel the charged particles 90 from movingradially past the border 36 toward the axis 38. The repelled chargedparticles 90 are attracted to the edge environ 48 with a force FS (notshown) and are effective to remove the undesired materials 50 from theedge environ 48, such as by sputtering.

FIG. 5 is a graph 100 showing field strength (i.e., strength of thefield 97 resulting from the field ring arrangement 96) vs. distance in adirection (e.g., of the paths 98 and 99) extending radially from theaxis 38. The distance is illustrated from the axis 38, outwardly to theleft past the border 36 and past the edge 44 of the substrate 30.Corresponding to one embodiment of the arrangement 96, the graph 100 isshown including a curve 100-1 representing a typical field 97 that is amagnetic field 97M having a field strength gradient G configured with apeak value P. Value P corresponds to the value of peak path 99, and thepeak path 99 extends adjacent to the border 36 (FIG. 4B). Correspondingto another embodiment of the arrangement 96, the graph 100 is shownincluding a curve 100-2 representing a typical field 97 that is anelectric field 97E having a field strength gradient G, and field 97E mayalso have a peak path 99 configured with the peak value P, the peak path99 also extending adjacent to the border 36. The exemplary curve 100-1representing the magnetic field embodiment of the arrangement 96 isshown having the field strength gradient G (referred to as GM) furtherconfigured with a slope S-1 extending from the peak value P (of peakpath 99 adjacent to the border 36). The exemplary curve 100-2representing the electric field embodiment of the arrangement 96 isshown having the field strength gradient G (referred to as GE) furtherconfigured with a slope S-2 extending from the peak value P (of therespective peak path 99 that is adjacent to the border 36). Slope S-1 isseen illustrated as being steep, or strong. In one sense, the steep orstrong slopes S-1 and S-2 indicate that the magnetic field strength ofthe field FM decreases suddenly from the peak value P with increaseddistance away from the border 36 and away from the axis 38. The suddendecrease may, for example, be from about ten kGauss (kG) per mm of suchdistance to about two kG per mm of such distance for slope S-1, and fromabout ten kG per mm of such distance to about one kG per mm of suchdistance for slope S-2. In a preferred embodiment of the slope S-1, thesudden decrease is about ten kG per mm of such distance. In anothersense, FIG. 5 shows that for the same change of distance (e.g., frompath 99 to path 98), the change of field strength per mm of suchdistance of slope S-1 is greater than the change of field strength ofslope S-2. The slope S-1 is said to indicate a steeper or stronger fieldstrength, such that the gradient GM of curve 100-1 is steeper orstronger relative to the gradient GE of curve 100-2.

FIG. 6 is a schematic elevational view showing one embodiment of themagnetic field embodiment of the arrangement 96, illustrating the first(lower) electrode 64 further configured with a first (or lower) fieldring mount section 110 extending radially from the border 36 and awayfrom the axis 38. In the magnetic field embodiment, the field ringarrangement 96 is configured with a ring-shaped permanent magnetarrangement 112. Arrangement 112 may be configured with a first (orlower) ring-shaped permanent magnet section 114 mounted in the first(lower) field ring mount section 110 of the first (lower) electrode 64.Arrangement 112 may also be configured with a second (upper) ring-shapedpermanent magnet section 116 mounted in the field ring mount section 94(also referred to as the second (upper) field ring mount section). Asshown in FIG. 6, the electrically grounded ring 182 is electricallyisolated from electrode 86 by insulator ring 187. The respective firstand second mounted ring-shaped permanent magnet sections 112 and 114 maybe configured to establish the field 97M as a magnetic field with theconfigured field strength gradient GM described by the exemplary graph100-1 (FIG. 5). It may be understood that the lower field ring mountsection 110 and the lower ring-shaped magnet section 114, as well as theupper mount section 94 and the upper ring-shaped magnet section 116,extend radially from the border 36 and away from the axis 38. Therespective first and second mounted ring-shaped permanent magnetsections 114 and 116 may be configured to establish the magnetic field97M having the peak path 99 extending directly between the first andsecond mounted permanent magnet sections 114 and 116. Field 97M includesmagnetic field lines 99M extending axially directly between therespective first and second mounted permanent magnet sections 114 and116. The respective ring-shaped sections 114 and 116 further establishthe field 97M as including return lines 98M of return path 98. Paths 98and 99 are annular paths centered on the axis 38. The respective firstand second mounted permanent magnet sections 114 and 116 are furtherconfigured to establish the magnetic field 97M configured with themagnetic field strength of each path 98 or 99, for example, that isuniform around the wafer axis 38 at a given radius relative to axis 38and that has the field strength gradient GM that varies with respect toradial distance of the path relative to the axis 38 and away from theborder 36 as shown by exemplary curve 100-1 in FIG. 5.

In one embodiment of the field ring arrangement 96 configured with thering-shaped permanent magnet arrangement 112, each magnet section 114and 116 may be configured with cross-sectional dimensions of 0.25 inchesby 0.75 inches, with the 0.25 inch dimension extending radially and withthe 0.75 inch dimension extending axially. Also, each ring magnetsection 114 and 116 may be configured as a NdFeB magnet providing an 11kG field strength, which for example may provide a 10 kG peak fieldstrength of path 99. In addition, each such magnet section may beconfigured with an inside radius of from about 0.25 to about 2 inchesfrom the axis 38 to the border 36, with an outside radius varyingaccording to the diameter of the substrate 30, e.g., 200 mm or 300 mm.Further, the section 116 may be a north pole of arrangement 112, and thesection 114 may be a south pole of arrangement 112. It may be understoodthat other dimensions, materials, and radii may be selected according tothe desired field strength, for example.

Referring again to FIG. 5, the embodiment shown in FIG. 6 may providethe field 97 as the magnetic field 97M having the characteristics shownin curve 100-1 that represents the field strength gradient GM for thefield 97M. The above exemplary inside radii of the rings 114 and 116 aremeasured to the border 36 so that the inside radii are verticallyaligned with the border 36, for example. The gradient GM definesmagnetic field strength that is inversely proportional to increasedradial distance of the exemplary paths 98 and 99 away from the axis 38(to the left in FIG. 5). The variation of the gradient GM is also fromthe peak value P of path 99 located adjacent to the border 36. Thegradient GM and the value of the peak P of the field strength areconfigured to repel the charged particles 90 from moving radially pastthe border 36 toward the axis 38. The repelled charged particles 90 areattracted to the edge environ 48 with the force FS that is effective toremove the undesired materials 50 from the edge environ 48, such as bysputtering.

The field strength gradient GM is further configured with the slope S-1extending from the peak value P (of path 99 that is adjacent to theborder 36), such that the strong gradient GM may be effective on thecharged particles 90 as described below. Because the ring-shaped magnetsections 114 and 116 are configured so that the field strength of themagnetic field FM is very low (e.g., less than 10 G) at return path 98at an exemplary radial distance of about twenty mm from the border(corresponding to a point 118), the magnetic field FM does not becomehighly effective on the charged particles 90 until the particles 90 arewithin the above-described range of about zero to 4 mm radially outwardfrom the border 36 (corresponding to the peak value of the peak path 99,FIG. 5), and at that peak value P of path 99 the field 97M is mosteffective and the particles 90 are suddenly repelled by the force FRfrom passing the border 36 and from moving further toward the axis 38.As a result, the charged particles 90 may be more and more acted on bythe field FM that applies the force FS to attract the particles 90toward the substrate 30 as the particles move radially inward toward theborder 36. In this manner, before more and more of the charged particles90 reach the border 36 such particles will bombard the edge environ 48,including bombarding the edge exclusion area 40, and will removeundesired materials 50 from the edge environ 48. Then, those chargedparticles 90 that reach the border 36 are suddenly repelled from passingthe border 36 and from moving further toward the axis 38, and willfurther bombard the edge environ 48 rather than moving further towardthe axis 38.

FIG. 7 is a schematic view similar to FIG. 6, showing an embodiment ofthe apparatus 60 wherein one or both of the respective first and secondring mount sections 110 and 94 is configured to adjustably mount therespective first and second permanent magnet sections 114 and 116 formovement relative to each other in a direction parallel to the axis 38(i.e., axially). In the axially adjustable magnetic field embodiment ofFIG. 7, the field ring arrangement 96 is configured with the ring-shapedpermanent magnet arrangement 112 (referred to as 112A) configured withthe first (or lower) ring-shaped permanent magnet section 114 mountedfor axial movement in the field ring mount section 110 (referred to as110A). The section 110A is configured to extend axially more than theaxial dimension of the first ring-shaped permanent magnet section 114.The section 110A is thus configured to permit the lower magnet section114 to be adjusted axially relative to the upper magnet section 116. Inone embodiment, the field ring arrangement 96 is configured so that thering-shaped permanent magnet arrangement 112A is configured with onlythe first ring-shaped permanent magnet section 114 mounted for axialmovement in the field ring mount section 110A, so that the second(upper) ring-shaped permanent magnet section 116 is fixed to electrode86. As shown in FIG. 7, the electrically grounded ring 182 iselectrically isolated from electrode 86 by insulator ring 187.

In another embodiment shown in FIG. 7, the field ring arrangement 96 isconfigured so that each of the respective lower and upper ring-shapedpermanent magnet sections 114 and 116 is mounted for axial movement.Thus FIG. 7 shows the field ring mount section 94 (referred to as 94A)configured to extend axially more than the axial dimension of the second(upper) ring-shaped permanent magnet section 116. The section 94A isthus configured to permit the upper magnet section 116 to be adjustedaxially relative to the lower magnet section 114. The section 110A isconfigured to extend axially more than the axial dimension of the firstring-shaped permanent magnet section 114. The section 110A is thusconfigured to permit the lower magnet section 114 to be adjusted axiallyrelative to the upper magnet section 116.

In yet another embodiment, the field ring arrangement 96 is configuredso that the ring-shaped permanent magnet arrangement 112A is configuredwith only the second (upper) ring-shaped permanent magnet section 116mounted for axial movement in the field ring mount section 94A, so thatthe first (lower) ring-shaped permanent magnet section 114 is fixed tothe mount 110.

In the various embodiments described with respect to FIG. 7, the axialadjustment of the respective first and second mounted ring-shapedpermanent magnet sections 114 and 116 may be by use of an adjustmentdevice 120. An exemplary device 120 is shown as a screw 122 configuredfor reception in a threaded hole 124 in the respective lower electrode64. Another exemplary device 120 is shown as a screw 126 configured forreception in a threaded hole 128 in the respective upper electrode 86.Adjustment of the appropriate exemplary screw 122 or 126, or of anotherconfiguration of the device 120, may be by a controller 130. Thecontroller 130 may be effective to adjust the configuration of the field97M (FIG. 6) to define the field as an axially-adjustable-strengthmagnetic field, referred to as 97MA-ADJ.

In one embodiment, the controller 130 may be a computer-controlled motor132 operated according to a recipe for the operation of removing theundesired material 50 from the edge environ 48. The field 97MA-ADJ maybe configured so that the field strength gradient G (referred to asGMADJ) is described by exemplary graphs 100-3, 100-4, and 100-5 in FIG.8. It may be understood that in the FIG. 7 embodiment, the lowerring-shaped magnet section 114, with the upper ring-shaped magnetsection 116, configure the field 97MA-ADJ (with the field strengthgradient GMADJ) to extend radially from the border 36 and away from theaxis 38. Also, once adjusted, the respective first and second sections114 and 116 are configured to establish the magnetic field 97MA-ADJextending between the respective first and second mounted permanentmagnet sections 114 and 116 in the same manner as described with respectto FIG. 6. For clarity of illustration, FIG. 7 does not show, but thefield 97MA-ADJ of FIG. 7 includes, the return path 98 and return lines98MA; and peak path 99, with magnetic field lines 99MA, that extendaxially directly between the respective first and second adjustablepermanent magnet sections 114 and 116. For the FIG. 7 embodiment, therespective ring-shaped sections 114 and 116 establish the field 97MA-ADJincluding those return lines 98MA of return path 98 and those magneticfield lines 99MA of peak path 99. The field 97MA-ADJ and paths 98M and99M are also annular, centered on the axis 38. The established magneticfield 97MA-ADJ is also configured with the magnetic field strength thatat a given radius is uniform around the wafer axis 38 and that has thefield strength gradient GMADJ that varies with respect to radialdistance of exemplary paths 98M and 99M relative to the axis 38 and awayfrom the border 36 as shown by the curves 100-3 to 100-5 in FIG. 8.

Referring to FIG. 8, generally, curves 100-3 to 100-5 show that a peakvalue PADJ (of path 99) of the field 97MA-ADJ may be adjusted, i.e.,controlled. As shown, exemplary adjustment may be that there is a higherpeak value P4 of curve 100-4 (dash-dash line) than peak P3 of curve100-3 (solid line), or there may be an exemplary lower peak value P5 ofcurve 100-5 (dot-dot line) than peak values P3 and P4. Different peakvalues PADJ may be obtained by using the controller 130 and motor 132 tocontrol rotation of the exemplary screws 122 or 126 to move either orboth of the sections 114 and/or 116 closer to the other section, forexample. This relative movement results in adjustment of the peak valueof the field strength gradient GMADJ of the peak path 99, e.g., as thesections 114 and 116 become closer the peak value PADJ may change fromP5, to P3, to P4. The reverse may be obtained by reverse rotation of thescrews to move either or both of the sections 114 and/or 116 furtherapart from the other section, for example.

As described above, the field strength of the magnetic field FM is verylow (e.g., less than 10 G) at the exemplary radial distance of abouttwenty mm of the exemplary path 98 from the border 36 (as shown in FIG.8 by the low points 118 of the curves 100-3 to 100-5). Also describedwas that the magnetic field FM does not become highly effective on thecharged particles 90 until the particles 90 are within theabove-described range of from about zero to about 4 mm radially outwardfrom the border 36 (corresponding to the peak values P3 to P5) of peakpath 99. The amount of the effectiveness of the magnetic field FMbecomes greater as the peak value P increases, and is thus highest bythe configuration of the sections 114 and 116 positioned axially closestto each other to provide the peak value P4 of the path 99 (as comparedto providing peak values P3 and P5 of path 99). Thus, such configurationproviding peak value P4 of path 99 will have the greatest illustratedeffectiveness on the particles 90 (as compared to peak values P3 or P5)so that with peak value P4 the particles will be subjected to astrongest repelling force FR most suddenly repelled (as compared to peakvalues P3 or P5) from passing the border 36 and from moving furthertoward the axis 38, and will be most attracted toward the substrate 30as the particles move radially inward toward the border 36 to path 99(as compared to peak values P3 or P5). In this manner, few of thecharged particles 90 will pass the border 36, providing a maximumprotection of the central area 32 and minimizing damage to the devices31 (as compared to peak values P3 or P5).

In one embodiment of the apparatus 60 also relating to FIG. 7, theconfiguration of the sections 114 and 116 positioned axially to providethe adjustable values of the peak magnetic field strength may be used toprovide protection for the central areas 32 when, for example, differentsubstrates 30 to be protected are configured with respective borders 36at different radial locations relative to the axis 38 of the respectivesubstrate. In this example, the respective borders 36 define differentradial extents of the central area 32 relative to the wafer edgeexclusion area 40, where the central area 32 is to be protected from thecharged particles 90. As described above, the configurations of therespective first and second ring mount sections 110 and 94 allowmovement of the respective first and second permanent magnet sections114 and 116 relative to each other in the axial direction to control thepeak value P of the magnetic field strength of the magnetic field FMaccording to the radial location of the border 36 with respect to theaxis 38. As described with respect to FIG. 8, for example, for the samepeak path 99, the adjustable mounting and movement may provide a lowerpeak value (e.g., P5) corresponding to an exemplary first radiallocation of the border 36 close to the axis 38, and may provide agreater peak value (e.g., P4) of the peak magnetic field strengthcorresponding to an exemplary second radial location of the border 36further away from the axis 38 than the first radial location. It may beunderstood that with the lower value of the peak P5, there is less forceFR (FIG. 4B) on the charged particles 90 and more time before the lowerpeak value P5 of the field acts on the charged particles 90. In thiscase, the particles 90 may travel longer radially inward toward axis 38.This longer travel is acceptable because the exemplary border 36 iscloser to the axis 38. It may be understood that with the higher peakvalue P4, there is more force FR on the charged particles 90 and lesstime before the peak value P4 of the field acts on the charged particles90. Thus, the particles 90 travel less radially inward (i.e., lesstoward the axis 38), which less travel is desired because the exemplaryborder 36 is further away from the axis 38.

In review, the configurations of the respective first and second ringmount sections 110 and 94 allow movement of the respective first andsecond permanent magnet sections 114 and 116 relative to each other inthe axial direction. That movement under the control of controller 130controls the peak value P of the magnetic field strength of the magneticfield FM in path 99 according to the radial location of the border 36with respect to the axis 38. As an illustration of the peak value Pbeing according to the radial location of the border 36 with respect tothe axis 38, for the path 99, the adjustable mounting and movementprovide a lower peak value (e.g., P5, FIG. 8) corresponding to anexemplary first radial location (e.g., 36-1, FIG. 8) of the border 36close to the axis and provide a greater value (e.g., P4) of the peakmagnetic field strength corresponding to a second radial location (e.g.,36-2 or 36-3, FIG. 8) of the border 36 further away from the axis 38than the first radial location 36-1. Thus, the reference to magneticfield strength of the magnetic field F “according to the radial locationof the border 36 with respect to the axis 38” describes the effect ofthe field FM for a given radii of the magnets relative to the centralaxis 38 (determined by the axial locations of the mount section 94 or110), and with a selected relative vertical spacing of sections 114 and116. This effect is to configure the field strength according to theexemplary different substrate configurations having the respectiveborder 36 at different radial locations (e.g., 36-1, 36-2, and 36-3),such that the charged particles 90 may be allowed to move radiallyinward across the edge exclusion area 40 by various distances beforebeing repelled by the force FR that is a maximum at the peak value P.

In one embodiment shown in FIG. 9, the apparatus 60 may be configured sothat the field strength is also controlled according to other substrateconfigurations. For example, another substrate configuration may be asfollows. The radial extent of the edge exclusion area 40 (that is not tobe protected and that is on the top surface 34 of the substrate 30) mayhave one value, a distance D1 radially in from the edge 44 and towardthe axis 38. There may also be a radial extent of the bottom surface 46(that is not to be protected), and this may have another value, adistance D2 radially in from the edge 44 to a perimeter 92. Distance D2is usually greater than distance D1. For these exemplary distances D1and D2, before being repelled by the force FR (FIG. 4B) that is amaximum at the peak value P, the charged particles 90 should be allowedto move radially inward across the bottom surface 46 toward the axis 38to the perimeter 92 through distance D2 that is greater than distanceD1. Distance D1 is the desired amount of movement of the particles 90radially in across the edge exclusion area 40 to the border 36 on topsurface 34.

FIG. 9 illustrates the configurations of the respective first and secondpermanent magnet sections 114 and 116 to control the location of thepeak path 99 of the magnetic field FM between the sections 114 and 116according to the desired extent of radial movement of the chargedparticles 90 across the respective top and bottom surfaces 34 and 46.The following is an illustration of the path 99 of the magnetic field FMbeing according to this desired extent of radial movement of the chargedparticles 90. With the sections 114 and 116 at a selected axialposition, one section, here shown as the exemplary lower section 114, isconfigured with a flux plate 150 secured to the section 114. The fluxplate may be an axially thin annular member extending radially from thesection 114. The flux plate 150 is fabricated from metal or othersuitable material so that the flux plate diverts the peak path 99 fromthat shown in FIG. 6, for example. FIG. 9 shows that the diverted peakpath 99 and the field lines 99MA in path 99 initially extend axiallyfrom the upper magnet section 116 and into the edge exclusion area 40 ofthe wafer 30 adjacent to the border 36. As the field lines 99MA of thepeak path 99 enter the edge exclusion area 40, the path 99 and lines99MA are redirected from axial into a redirected path 152 that extendsradially and axially through the wafer 30 and diagonally toward the axis38 and across a space 154 between the sections 114 and 116. Theredirected path 152 extends axially past (and radially outside of) theperimeter 92 to the flux plate 150 attached to the lower section 114.Thus, the flux plate 150 is configured to redirect the field FM from thedirect axial path 99 (shown in FIGS. 6 and 8), and into the describedredirected path 152. Since the perimeter 92 is radially toward the axis38 more than the border 36, the redirected path 152 thus extends closerto the axis 38 under the substrate 30 than above the substrate. Thus,the flux plate 150 is effective below the substrate 30 to position thepeak field strength FM radially in with respect to the border 36. Theflux plate 150 is also configured with a radial length to select anamount of the radial redirection (or diversion) of the path 152 so as tolocate the peak value P of the radially diverted magnetic field FM (inpath 152) at a selectable radial location relative to the axis 38. Anexemplary radial location is identified as RL. It may be understood,then, that the flux plate 150 is configured to locate the peak path 99of the field strength according to the exemplary different substrateconfigurations that require the particles 90 to bombard the surfaces 34and 46 at different radial locations relative to the axis 38. Accordingto the configuration of the flux plate, charged particles 90 may thus beallowed to move radially inward toward the axis 38 by different radialdistances. Thus, particles 90T may move a different radial distanceacross the top surface 34 than particles 90B move across the bottomsurface 46 before being repelled by the force FR that is a maximum atthe peak value P.

In review, by the configuration of the flux plate 150, the apparatus 60is configured for protecting different substrates 30, the differentsubstrates being configured with the border 36 and the perimeter 92 atdifferent radial locations relative to the axis 38 of the respectivesubstrate. The different radial locations of the border 36 are indicatedby the above-described distance D1, for example, and the differentradial locations of the perimeter 92 are indicated by theabove-described distance D2, for example. The flux plate 150 is thusconfigured to radially divert the peak path 99 of the axially extendingmagnetic field MF so that the amount of the radial diversion locates thepeak value P of the radially diverted magnetic field MF according to theradial location of the border 36 of one of the different substratesrelative to the axis 38, and according to the radial location of theperimeter 92 on the bottom 46 of the wafer 30.

As described above, FIG. 3 shows the upper electrode 86 configured withthe field ring mount section 94, and the field ring arrangement 96configured to establish the field 97 having a return path 98 and a peakpath 99. FIG. 10 shows another embodiment of the apparatus 60 of FIG. 3,in which the field ring mount section 94 and the field ring arrangement96 may be configured for protecting the central area 32 of the substrate30 from the charged particles 90 in the process chamber 62. The first(lower) electrode 64 is configured to mount the substrate 30 asdescribed above, and the border 36 may be configurable at any of aplurality of radial distances relative to the axis 38. The firstelectrode 64 is configured with a first electrically grounded ring 180extending in an annular path radially outward of the edge exclusion area40 (away from axis 38) and electrically isolated from the wafer support64 by an insulator ring 187 a. Different configurations of the edgeexclusion area 40 may be defined by the border 36 positioned atdifferent ones of a plurality of radial distances relative to the axis38. The second (or upper) electrode 86 is configured with the annularmount section 94 aligned with the border 36. The second electrode 86 isfurther configured with a second electrically grounded ring 182extending in an annular path radially outward of the edge exclusion area40 and electrically isolated from the center area 32 and from the firstannular mount section 94 by an insulator ring 187 b. The first annularmount section 94 is electrically isolated from the center area 32 aswell. The field ring arrangement 96 may be configured with a DC biasring 186 secured to the first annular mount section 94 to establish theelectric field FE in the process chamber 62. The DC bias ring 186 isconfigured so that the electric field FE extends away from the circularborder 32 and across the edge exclusion area (bracket 40) to each of therespective first and second grounded rings 180 and 182 to repel thecharged particles 90 from crossing the border 36 and to promote etchingof the edge exclusion area 40. The field ring arrangement 96 may beconfigured further with a DC control circuit 190 for applying a DCvoltage to the DC bias ring 186. The circuit 190 is configured so thatthe DC bias ring applies a positive DC voltage to establish the electricfield FE. The positive DC voltage establishes the electric field FE andrepels positively charged particles 90 from crossing the border 36 andpromotes etching of the edge exclusion area 48 by the repelledpositively charged particles 90. For a particular value of a distance192 between the wafer 30 and the ring 186, a value of the positive DCvoltage may be directly proportional to a value of the radial distanceof the border 36 relative to the axis 38. For example, the positive DCbias voltage may be in a range of from about one volt to about 200 voltswhen distance 192 is about one mil.

In one embodiment, the DC control circuit 190 is configured for applyingdifferent DC voltages to the DC bias ring 186 to establish differentstrengths of the electric field FE. A first strength may have a firstvalue corresponding to a first of the radial distances, and a secondstrength having a second value corresponding to a second of the radialdistances. The second radial distance is further away from the axis 38than the first radial distance, and the second value exceeds the firstvalue.

In another embodiment, the first annular mount section 94 extends in acircular path opposite to the annular edge exclusion area 40. Also, theDC bias ring 186 is configured so that the electric field FE extendsradially away from the circular border 36 and all around the edgeexclusion area 40 so that the movement of the charged particles 90across the border 36 is repelled all around the border and bombardmentof the edge exclusion area 40 by the repelled particles 90 is promotedall around the edge exclusion area 40. The electric field FE may be asshown in FIG. 5 by curve 100-2.

FIG. 11 is a diagram showing a flow chart 200, illustrating operationsof a method of protecting a central area of a wafer from chargedparticles during etching of an edge exclusion area surrounding acircular border that defines the central area. The central area may bearea 32 of the substrate 30, and the charged particles may be particles90 that occur during etching of the edge exclusion area 40 surroundingthe circular border 36 that defines the central area 32. The method maymove from start to an operation 202 of mounting the wafer in an etchingchamber with the edge exclusion area extending in a radial directionoutside a border that defines a central device area to be protected. Themounting may be as shown in any of FIG. 6, 7 or 9, for example. Thewafer 30 is thus mounted in the etching chamber 62 with the edgeexclusion area 40 extending in the radial direction outside the border36 and perpendicular to the axis 36. The method may move to an operation204 of establishing a constant magnetic field between opposite permanentmagnet polarities. The establishing configures the magnetic field toprovide a peak value of magnetic field strength that is adjacent to theborder. The magnetic field strength of the established magnetic fielddecreases suddenly from the peak value with increased distance away fromthe border and from the axis. The peak value of the magnetic field andsudden decrease of the magnetic field strength repel movement of chargedparticles past the border to the central region and promote bombardmentof the edge exclusion area by the repelled particles. The establishingof the constant magnetic field between opposite permanent magnetpolarities relates to the field FM at the exemplary peak value P ofgraph 100-1 in FIG. 5, for example. As described in respect to FIGS. 5and 6, for example, the establishing provides the peak value P ofmagnetic field strength that is adjacent to the border 36. The magneticfield strength of the field FM is shown in FIG. 5 decreasing suddenlyfrom the peak value P with increased distance away from the border 36and away from the axis 38. As described above, the peak value P of themagnetic field FM and the sudden decrease of the magnetic field strengthrepel movement (FIG. 4B, arrow 206) of charged particles 90 past theborder 36 to the central region 32 and promote bombardment of the edgeexclusion area 40 by the repelled particles 90. The method is then done.

In one embodiment shown in flow chart 210 of FIG. 12, the method maycontrol the value of the peak magnetic field strength of the magneticfield, wherein the magnetic field extends through the wafer at the edgeexclusion area, and wherein the control of the value is according to aradial location of the border with respect to a central axis of thewafer. The control of the value may be of the peak value P (FIG. 5) ofthe strength of the magnetic field FM. The field FM may extend axiallythrough the wafer 30 as shown in FIG. 6, for example. The peak value Pmay be controlled according to the radial location of the border 36. Asdescribed above, the location of the border is a radial location withrespect to the central axis 38 of the wafer 30, such that the radiallocation may be measured from the axis 38 radially outwardly toward theedge 44. FIG. 12 shows the flow chart 210 illustrating further aspectsof operation 204 for controlling the peak value P. The method moves fromoperation 202 to operation 204. Operation 204 is first performed by afurther operation 212 of configuring each of two opposite polaritypermanent magnet sections with an annular-shape, one magnet sectionextending on each side of the wafer. The configuring may be of theexemplary ring-shaped north polarity of permanent magnet section 116 andof the exemplary ring-shaped south polarity of section 114. As describedabove and shown in FIGS. 1 and 6, each section 114 and 116 is configuredwith an annular (i.e., ring) shape. FIGS. 6 and 7, for example, show thesection 114 on one side (lower) of the wafer 30, and the section 116 onthe other side (upper) of the wafer 30.

The method moves to a further operation 214 of positioning the oppositepolarity permanent magnets spaced relative to each other by a distancethat extends parallel to the wafer axis, the positioning being accordingto the radial location of the border of the respective wafer. Byreference to the above description of FIG. 8, the positioning of themagnets according to the radial location of the border of the respectivewafer may be understood. For the same peak path 99 of the magnetic fieldFM, the adjustable mounting and axial relative movement of the magnetsections 114 and 116 may provide a lower peak value (e.g., P5)corresponding to an exemplary first radial location of the border 36close to the axis 38, and may provide a greater value (e.g., P4) of thepeak magnetic field strength corresponding to an exemplary second radiallocation of the border 36 further away from the axis 38 than the firstradial location. By reference to FIG. 5, it may be understood that inthe various axial positions of the sections 114 and 116, the magneticfield strength decreases suddenly from the peak value P adjacent to theborder 36. Also, by reference to FIG. 7, for example, it may beunderstood that the positioning may be positioning of the oppositepolarity permanent magnet sections 114 and 116 spaced relative to eachother, and the spacing is by a vertical (i.e., axial) distance extendingparallel to the wafer axis 38. The method is then done.

FIG. 13 illustrates one embodiment of a method that is described by aflow chart 230. The method may control the location of a peak path ofthe magnetic field between sections of the magnets according to adesired extent of radial movement of the charged particles across topand bottom surfaces of the wafer. The location controlled may be thelocation of the peak path 99 of the magnetic field FM between the magnetsections 114 and 116 according to the desired extent of radial movementof the charged particles 90 across the respective top and bottomsurfaces 34 and 46 of the wafer 30. Thus, in the controlled location,the field FM in peak path 99 may protect different areas of the top andbottom surfaces 34 and 45 of the wafer 30 from charged particles 90 inthe process chamber 62.

FIG. 13 shows that the method may move from start to an operation 232 ofmounting a wafer that is configured so that a border is spaced from anedge of the wafer by a distance of an edge exclusion area, the waferbeing configured with a bottom surface having a perimeter at a locationfurther from the edge than the border and toward a central axis of thewafer. The wafer may be the wafer 30 (FIG. 1) configured so that theborder 36 is spaced from the edge 44 of the wafer by a radial distance(e.g., D1) relating to the edge exclusion area 40 and the bevel 42. Thewafer 30 may be configured with the bottom surface 46 having theperimeter 92 (FIG. 9) at a location further from the edge 44 than theborder 36 (i.e., more toward the central axis 38 of the wafer 30 thanthe border). Thus, as shown in FIG. 9, the bottom area between the bevel42 and the perimeter 92 may be greater than the edge exclusion area 40between the border 36 and the bevel 42 near the edge 44, yet both suchareas are to be protected. The method may move to operation 234 ofestablishing a magnetic field by aligning the opposite polaritypermanent magnets along a line adjacent to the border so that a peakpath of a peak value of the magnetic field is adjacent to the border.The magnetic field strength may decrease suddenly from the peak valuewith increased distance away from the border and from the axis. Theoperation 234 of establishing the magnetic field between oppositepermanent magnet polarities may relate to the field FM at the exemplarypeak value P of graph 100-1 in FIG. 5, for example. As described inrespect to FIGS. 5 and 6, for example, the establishing provides thepeak value P of magnetic field strength of the peak path 99 that isadjacent to the border 36. The magnetic field strength of the field FMis shown in FIG. 5 decreasing suddenly from the peak value P withincreased distance away from the border 36 and away from the axis 38.The path 99 of the peak magnetic field FM may originate as an axiallyextending path that is vertically aligned with the upper magneticsection 116 as shown in FIG. 9, for example.

The method may move to operation 236 of redirecting a portion of thepath of the peak value of the magnetic field so that the path extendsfrom adjacent to the border and then radially and axially toward theaxis and under the bottom of the substrate to the perimeter. Themagnetic field strength may decrease suddenly from the peak value withincreased distance away from the path, i.e., away from the path thatextends between the perimeter and the border. The redirecting may be ofthe portion 152 of the path 99 of the peak value P of the magnetic fieldFM. The redirecting may be as shown in FIG. 9, in which the peak path 99extends initially axially from the upper magnet section 116 and into theedge exclusion area 40 of the wafer 30 adjacent to the border 36. Thepath 99 and lines are redirected from axial into the redirected path 152that extends radially and axially through the wafer 30, diagonallytoward the axis 38 and across the space 154 and past the perimeter 92 tothe flux plate 150.

In review, by the configuration of the flux plate 150, the apparatus 60is configured for protecting different substrates 30, the differentsubstrates being configured with the border 36 and the perimeter 92 atdifferent radial locations relative to the axis 38 of the respectivesubstrate. The different radial locations of the border 36 are indicatedby the above-described distance D1, for example, and the differentradial locations of the perimeter 92 are indicated by theabove-described distance D2, for example. The flux plate 150 is thusconfigured to radially divert the peak path 99 of the axially extendingmagnetic field MF so that the amount of the radial diversion locates thepeak value P of the radially diverted magnetic field MF according to theradial location of the border 36 of one of the different substratesrelative to the axis 38, and according to the radial location of theperimeter 92 on the bottom 46 of the wafer 30.

In view of the above descriptions, it may be understood that the variousembodiments of the present invention provide ways of protecting thecentral area 32 so that during the removing of the undesired materials50 from the edge environ 48 the central area is not damaged, i.e., theremoval is only from the edge environ 48. Also, by selecting oneembodiment of the arrangement 96, e.g., the magnet sections 114 and 116,these sections provide characteristics of the typical field 97 as shownin curve 100-1 for the magnetic field 97M. The field 97M has the fieldstrength gradient GM configured with the peak path 99 having the peakvalue P, and the path 99 extends adjacent to the border 36. By selectinganother embodiment of the arrangement 96, e.g., the DC bias ring 186,the ring provides characteristics of another typical field 97 as shownin curve 100-2 for the electric field 97E. Field 97E has the fieldstrength gradient GE also configured with the peak path 99 configuredwith the peak value P, and the path 99 also extending adjacent to theborder 36.

The exemplary curve 100-1 representing the magnetic field embodiment ofthe arrangement 96 is shown having the field strength gradient GMfurther configured with the slope S-1 extending from the peak value P(of path 99 adjacent to the border 36). Slope S-1 is seen illustrated asbeing steep, or strong, as defined above, in that for the same change ofdistance (e.g., from path 99 to path 98), the change of field strengthof slope S-1 is greater than the change of field strength of slope S-2.

In the embodiment of FIG. 6, and in the embodiment of the method of FIG.11, the first and second mounted ring-shaped permanent magnet sections114 and 116 are configured to establish the magnetic field 97M havingthe peak path 99 extending directly between the first and second mountedpermanent magnet sections 114 and 116. Magnetic field lines 99MA extendaxially (parallel to the axis 38) directly between the first and secondmounted permanent magnet sections 114 and 116. The ring-shaped sections114 and 116 further establish the field 97M uniform around the waferaxis 38 and having the field strength gradient GM varying with respectto radial distance of the path relative to the axis 38 and away from theborder 36 as shown by curve 100-1 in FIG. 5.

FIGS. 7 and 8 show that the field 97MA-ADJ may be configured so that thefield strength gradient GADJ is described by exemplary graphs 100-3,100-4, and 100-5 (FIG. 8), illustrating control of variable peak fieldstrength by way of relative axial positioning of the lower ring-shapedmagnet section 114 with respect to the upper ring-shaped magnet section116. The field 97A-ADJ (with the field strength gradient GADJ) is alsoconfigured to extend radially from the border 36 and away from the axis38, with the magnetic field 97MA-ADJ extending between the first andsecond mounted permanent magnet sections 114 and 116. The field 97MA-ADJincludes peak path 99 with magnetic field lines 99MA extending axially(parallel to the axis 38) directly between the first and secondadjustable permanent magnet sections 114 and 116. The field 97MA-ADJ andpaths 98 and 99 are also annular and uniform around the wafer axis 38and that has the field strength gradient GMADJ that varies with respectto radial distance of exemplary paths 98 and 99 relative to the axis 38and away from the border 36 as shown by the curves 100-3 to 100-5 inFIG. 8.

For any given peak path 99, there may be control of the value of thepeak field strength. In a method aspect of this axial positioning,operation 214 (FIG. 12) positions the opposite polarity permanentmagnets 114 and 116 spaced relative to each other by a distance thatextends parallel to the wafer axis 38. The positioning is according tothe radial location of the border 36 of the respective wafer 30. Thus,for the same radial location of the peak path 99 of the magnetic fieldFM, the adjustable mounting and axial relative movement of the magnetsections 114 and 116 may provide the lower peak value (e.g., P5)corresponding to the exemplary first radial location 36-1 of the border36 closest to the axis 38, and may provide the exemplary greatest value(e.g., P4) of the peak magnetic field strength corresponding to theexemplary third radial location 36-3 of the border 36 further away fromthe axis 38 (i.e., than the first and second radial locations.

Although a few embodiments of the present invention have been describedin detail herein, it should be understood, by those of ordinary skill,that the present invention may be embodied in many other specific formswithout departing from the spirit or scope of the invention. Therefore,the present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details provided therein, but may be modified and practicedwithin the scope of the appended claims.

What is claimed is:
 1. A chamber for processing a bevel edge of asubstrate, comprising: a bottom electrode defined to support a substratein the chamber, the bottom electrode having a bottom first level forsupporting the substrate and a bottom second level near an outer edge ofbottom electrode, the bottom second level defined at a step below thebottom first level; a top electrode oriented above the bottom electrode,the top electrode having a top first level and a top second level, thetop first level being opposite the bottom first level and the top secondlevel being opposite the bottom second level, the top second leveldefined at a step above the top first level; a bottom grounded electrodedisposed around the bottom electrode at the bottom second level; a topgrounded electrode disposed around the top electrode at the top secondlevel; a bottom ring mount oriented at the bottom second level, thebottom ring mount supporting a bottom permanent magnet; and a top ringmount oriented at the top second level, the top ring mount supporting atop permanent magnet, the top permanent magnet being oriented oppositethe bottom permanent magnet.
 2. The chamber of claim 1, wherein the topand bottom permanent magnets are one of a south pole magnet and one of anorth pole magnet.
 3. The chamber of claim 1, wherein the top secondlevel and the bottom second level are opposite of each other, and definea region for plasma etching of the substrate edge when present.
 4. Thechamber of claim 1, further comprising a first RF power connection tothe top electrode and a second RF power connection to the bottomelectrode.
 5. The chamber of claim 1, wherein the bottom groundedelectrode is ring shaped.
 6. The chamber of claim 5, wherein the topgrounded electrode is ring shaped.
 7. The chamber of claim 1, wherein afirst insulator ring is disposed between the bottom electrode and thebottom grounded electrode, and a second insulator ring is disposedbetween the top electrode and the top grounded electrode.
 8. The chamberof claim 1, wherein the bottom permanent magnet is adjustably mounted inthe bottom ring mount to allow the bottom permanent magnet to beadjusted axially relative to the top permanent magnet.
 9. The chamber ofclaim 1, wherein the top permanent magnet is adjustably mounted in thetop ring mount to allow the top permanent magnet to be adjusted axiallyrelative to the bottom permanent magnet.
 10. The chamber of claim 1,wherein the top permanent magnet is adjustably mounted in the top ringmount to allow the top permanent magnet to be adjusted axially relativeto the bottom permanent magnet, and the bottom permanent magnet isadjustably mounted in the bottom ring mount to allow the bottompermanent magnet to be adjusted axially relative to the top permanentmagnet.
 11. A chamber for etching a bevel edge of a substrate,comprising: a lower electrode defined to support a substrate in thechamber for plasma etching when powered, the lower electrode having afirst level for supporting the substrate and a second level near anouter edge of lower electrode, the second level defined at a step belowthe first level; an upper electrode oriented above the lower electrode,the upper electrode having a first level and a second level, the firstlevel of the upper electrode being opposite the first level of the lowerelectrode and the second level of the upper electrode being opposite thesecond level of the lower electrode, the second level of upper electrodedefined at a step above the first level of the upper electrode; a bottomgrounded electrode disposed around the lower electrode at the secondlevel of the lower electrode; a top grounded electrode disposed aroundthe upper electrode at the second level of the upper electrode; a lowerring mount oriented at the second level of the lower electrode, thelower ring mount supporting a bottom permanent magnet; and an upper ringmount oriented at the second level of the upper electrode, the upperring mount supporting a top permanent magnet, the top permanent magnetbeing oriented opposite the bottom permanent magnet.
 12. The chamber ofclaim 11, wherein a separation between the first levels of the upper andlower electrodes is less than a separation between the second levels ofthe upper and lower electrodes.
 13. The chamber of claim 11, wherein aregion for plasma etching of a substrate edge, when the substrate ispresent, is defined between the second levels of the upper and lowerelectrodes.
 14. The chamber of claim 11, further comprising a first RFpower connection to the upper electrode and a second RF power connectionto the lower electrode.
 15. The chamber of claim 11, wherein the bottomgrounded electrode is ring shaped.
 16. The chamber of claim 15, whereinthe top grounded electrode is ring shaped.
 17. The chamber of claim 11,wherein a first insulator ring is disposed between the bottom electrodeand the bottom grounded electrode, and a second insulator ring isdisposed between the top electrode and the top grounded electrode.
 18. Achamber for processing a bevel edge of a substrate, comprising: a bottomelectrode defined to support a substrate in the chamber, the bottomelectrode having a bottom first level for supporting the substrate and abottom second level near an outer edge of bottom electrode, the bottomsecond level defined at a step below the bottom first level; a topelectrode oriented above the bottom electrode, the top electrode havinga top first level and a top second level, the top first level beingopposite the bottom first level and the top second level being oppositethe bottom second level, the top second level defined at a step abovethe top first level; a bottom grounded electrode disposed around thebottom electrode at the bottom second level; a top grounded electrodedisposed around the top electrode at the top second level; a top ringmount oriented at the top second level, the top ring mount supporting atop permanent magnet; and a bottom ring mount oriented at the bottomsecond level, the bottom ring mount supporting a bottom permanentmagnet, the bottom permanent magnet being oriented opposite the toppermanent magnet, wherein one of the top ring mount or the bottom ringmount is configured to allow one of the respective top and bottompermanent magnets to be adjusted relative the other of the respectivetop and bottom permanent magnets.
 19. The chamber of claim 18, whereinthe bottom ring mount is configured to allow the bottom permanent magnetto be adjusted relative to the top permanent magnet.
 20. The chamber ofclaim 18, wherein the top ring mount is configured to allow the toppermanent magnet to be adjusted relative to the bottom permanent magnet.